The conventional transmission device for scanner with high/low resolution option generally uses micro-step means to drive motor for obtaining high resolution. For examples, the micro-step means can be single step for 300 dpi, half step for 600 dpi, 1/4 step for 1200 dpi and 1/8 step for 2400 dpi resolution. However, the motor has best rotation accuracy for single step because two phases are simultaneously magnetically excited. The motor has less rotation accuracy for half step operation because one/two phases magnetically excited are alternatively performed. For 1/4 step or 1/8 step operation, voltage difference magnetically excited are used, thus degrading the accuracy, especially for the high-resolution printing such as above 1200 dpi. Therefore, the registration is influenced. The scanner can not have high scanning speed or need larger motor torque for scanning in low-resolution mode when single step operation is used.
It is an object of the present invention to provide a change gear transmission device for scanner with high/low resolution option, by which the high speed and high accuracy performance is achieved.
To achieve above object, the present invention provides a change gear transmission device for a scanner comprising a motor, a first gear, a second gear and a third gear. The second gear and the third gear are movably arranged within the scanner and can be moved in axial direction. The first gear is connected to the axis of motor. The second gear and the third gear are arranged on one end of the driving shaft of the scanner and have different tooth number. The first gear is optionally engaged with the second gear or the third gear by the movement of the second gear and the third gear. Therefore, the inventive change gear transmission device can provide both high speed and high accuracy ability to the scanner with low/high resolution.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which: